Researchers in demography have developed a new model that provides more accurate estimates of population sizes than the models currently used by government organisations. This alternative method has the potential to affect policy decisions, according to Elenora Mussino, one of the researchers behind the study.
Current methods for population size estimation rely heavily on information in population registers. If individuals who have left the country or passed away remain listed in some registers, it can lead to an overestimation of the population size. This error can have negative societal effects.
– For example, it can look like inactivity of migrants is higher than it is, or that the fertility is lower than it is. This can affect the public narrative, which in turn can lead to other consequences like policy decisions, says Eleonora Mussino.
Eleonora Mussino. Photo: Leila Zoubir
The new method, developed by Eleonora Mussino and her collegues, is better than the traditional one since it takes uncertainty into account. It is motivated by models developed for monitoring wildlife populations and uses different registers to estimate the probability that a person visible in the registers is still alive or in the country.
– In the traditional model you can say I’m right, but you might actually be bringing in an error. Our method is probabilistic and accepts that there is uncertainty and observation error in the register data.
An important extension of the approach is that it assigns a probability value to all possible migration movements, including leaving and re-entering the country or de-registering upon departure. By incorporating uncertainty measures into each stage of the migration process, the model can capture the full life cycle of a migrant’s presence in Sweden from the moment they arrive.
The new method has already invoked interest from government organisations and it will be tested in an upcoming project lead by Eleonora Mussino.
The Department of Sociology is home to the Stockholm University Demography Unit (SUDA), an international group of scholars and doctoral students, working on many facets of population dynamics. It offers a Master’s program in Demography and a PhD program in Sociological Demography.
